lift pump question

[Kurt Henzler]

what is in charge of filling the fuel canister with fuel. i can hear the pump running, sounds like it is on the back of the canister that holds the fuel filter. a dealer just told me that the pump will not fill the fuel canister with the lid on because there is no place for the air to go. is this true. if am not getting fuel into the fuel canister.

 

[robobx]

damn good question!



not to hijack the thread, but while we're on the subject...

without a fuel pressure guage, how do you know when your lift pump has gone bad???



Thanks!!!

Rob

 

[rashwor]

Rob...

you don't know without a gauge.

 

[DPelletier]

the only good thing is that it doesn't matter if the lift pump fails or not. Truck will run fine without it and it won't hurt the HPCR unlike the VP44. My understanding is that the lift pump only prevents having to bleed the system in the event you run out of fuel, as well as helping the HPCR build pressure faster for start-up.



Sorry Kurt, I don't know the answer to your fuel canister question.

Dave

 

[Prairie Dog]

I don't know where the air goes but I just tighten it all up dry and cycle the key 3 or 4 times. It lights rite off w/o any stumble.

 

[krabman]

Having tried to run the truck without it I can tell you that it will not run fine without it. Yes I am aware that the EU trucks run sans lift pump and so do the duramax's. Those are different setups than you have on your truck. The cp3 will starve without the liftpump on our trucks. Even stock ones. I have yet to read from any credable source exactly what impact starving the cp3 has long term but I do know I dont want to buy one. If your lift pump goes out your truck will not start. Im not sure how you could tell if it was weak.

 

[DPelletier]

Krabman,

I will defer to your thoughts on this issue, as you definitely know more about it than I. I will also spare you from me reiterating the entire context of the message that Cummins gave us via Robyn (TDR Admin) away back when. Cummins basically was telling us that the truck would run without a lift pump as long as it didn't lose prime. I also know alot of people are skeptical of this and that if the engine is modified and the fueling increased, lift pump pressure (or probably more correctly, volume) seems to become a bigger issue.

What I would like to know is two things;



- 1) What exactly (other than the lift pump vs. a hand priming pump) is different in our HPCR design vs. the european HPCR?



- 2) Has anyone heard of a CP3 (HPCR pump) being damaged by low fuel pressures.



Thanks

Dave

 

[robobx]

So it sounds like, to me. You will not know if you have a weak lift pump, but you'll know when the lift pump does not work at all when you change your fuel filter and the canister does not fill up and the truck doesn't start...



Am I looking at it wrong? or does this sound about right?

 

[DCTECH]

The air is bleed out through the injectors. If you have the key on the injectors start clicking to purge out air because ECM did not see engine start.

 

[DPelletier]

robobx,

I dunno for sure, but that sounds right to me. You may also get an indication that the lift pump is weak/dead if the truck stumbles on sustained full throttle, full load applications. Course, Cummins says this shouldn't happen.



DCTECH,

I understand that the injectors purge the air, but you need lift (transfer) pump volume to fill the system, right?



Dave

 

[RankRam]

Originally posted by DCTECH

The air is bleed out through the injectors. If you have the key on the injectors start clicking to purge out air because ECM did not see engine start.

Thanks for that little piece of info! I was wondering what the clicking was. I was thinking it was the cam sensor.

 

[krabman]

As I said I have yet to read from a reliable source what possible damage may occur if any by starvation of the cp3. I did read the post by Robyn. I also tried it myself. We spent the better part of a day in the shop trying to run my truck sans lift pump. We failed. I would suggest calling one of the experts in the field like Keith at DD if it makes you feel more comfortable and getting it straight from the horses mouth. Rod at Wildcat has also spent alot of time on this and he could also give you some insight on the fuel system. For myself I have to believe what I saw in the real world on a real truck.

 

[DPelletier]

Krabman,

Sorry if it sounded like I was being sarcastic, that wasn't my intent. Sometimes it is hard to infer people's emotional content in these threads. Anyway, I don't dispute your results and I have also read all the other threads. It does appear that the lift pump operation is more important that Cummins would have you believe.

However, I am not sure we are in the same position that we were with our lift pump /VP44 situation. On the 24valves, we were in real danger of having terminal injectionpumpitis in the event of a lift pump failure. We also had lift pumps dropping like flies (did one on my '01 @ 45,000 mi). What I'd really like to know is if our current "lift pump" is more reliable than the old one, and whether or not the HPCR system is subject to terminal damage in the event the lift pump fails. Or, is it going to be like; " my truck is stumbling on sustained full load, full throttle applications, time to change the lift pump " with no disasterous harm done.

As you've said, you haven't heard yet and are erring on the side of caution. This is the right thing to do as I'm not even aware of the cost of a CP3. Hopefully the lack of CP3's littering the landfills is a testament to thier fortitude. time will tell.

I am also truly interested in the european set-up. If they can run w/o a pump, then it is possible to make a system that doesn't depend on it.



Cheers

Dave

 

[robobx]

Please forgive me, I learn by seeing... How hard is it to put in a fuel pressure guage? are there any write ups on the web?(I haven't found any yet) Do they come with really good instructions? on my TJ I'll try about anything, but on this truck I'm much more cautious, don't have an extra few K laying around if I royally screw something up on this bugger.



Thanks for the help!!!

Rob

 

[krabman]

It was Rod who explained the differences in the fuel systems to me. I haven't myself so much as looked under the hood of a duramax truck. We were installing my pusher pump kit when we figured out that the supplied pump came DOA. We had a few hours to kill waiting for the new pump to be dropped off and I brought up the subject of why cant we get the truck running without it? We had all read the same material (Robyns's post and others like it) and there was a group "yea why cant we". With time on our hands and curiosity piqued we began the sans lift pump cummins battle. We did get the truck to light up after considerable effort but could not get it to run correctly. None of us knew what if anything we might be hurting in regards to the cp3 or other parts but we were all in agreement that we didn't want to find out how much those parts might cost. So we figured discretion would be wise and gave it up. That was some time ago and now there is more information out there. It is pretty much proved out that you need your lift pump. The truck will not make any more power when your pressure drops to zero. Keep it there and your truck will stall from fuel starvation. If you should talk to Rod ask him about stalling his out on the freeway. Clearly the pump is more important as you said than DC first led us all to believe. A question I ask is why is it there at all if its not really needed? I know Dodges answer but does it make sense? I also would love to know if I could drive home in a limp mode fashion if my pusher failed without concern over the cp3 taking possible damage. Anyhow I am not one of the experts I'm just relaying my experience with it. For all I know it could be something as simple as our trucks having a more restrictive fuel filter. I didn't take your post as sarcastic, they is a lot of stuff out there in this regard and the more we all share information the sooner we will get to the truth.

 

[Mopar_Mudder]

krabman,



When you tried to run without the pump did you by-pass it all together. I have kind of thought that the problem with running out of fuel is that the CP3 could suck its own fuel if it had the plumbing to do so. Maybe the lift pump creates a restrition that the CP3 can't suck enough volume through. The lift pump is on the filter housing, not in the tank, correct?



Personally I have had good fuel pressure running the EZ on level 4, guess I am one of the luckier ones.

 

[krabman]

Its on the back side of the filter housing. We had it off and plumbed direct. We first tried to see if the cp3 could prime itself but that didn't fly. We then tried priming it. Our first attempt provided 2 psi of pressure and we couldn't get it to light off. It would cough and sputter but that was it. Our second attempt came with a 5 psi prime and this did get the truck started but it would not run cleanly. Tried keeping the rpms up to 1300 for a while to see if it would clean up but it did not. Most of our time was spent just trying to get the fuel system primed since we didn't have the bulb or plunger or whatever mechanism a duramax uses to do the job. It is possible that following a procedure we did not know you could get the truck up and running. As I said I'm not one of the smart guys and the possibility cant be dismissed. It doesn't however look to me like the average guy stuck somewhere with a dead lift pump is going to have an easy time getting his truck started.

 

[Agades]

how did you plumb it direct?



does the lift pump thread into the can or just a push in O-ring type fitting



I guess what Im getting at is what kind of fitting would it require to plumb into the can without the factory lift pump?

 

[krabman]

O-ring, couple of allen bolts and its off. The DD kit has a little custum fitting to put in place after the lift pump comes off. It was this fitting we used.

 

[Agades]

does the DD kit eliminate the stock lift pump ?



Id like to see something like that.

up here in salt central a pusher pump down by the tank just takes a beating so Id like to run a good pump under the hood away from road spray



ive been meaning to take my lift pump off and possibly machine out whatever necessary but been too busy with other stuff